This invention relates to water pumps of the centrifugal impeller type intended primarily for use in diesel engine cooling systems, especially for railroad locomotives, but also useful for other purposes.
It is known in the art relating to diesel engine cooling systems to provide an engine with one or more centrifugal water pumps, each having a centrifugal flow or mixed flow impeller carried on a shaft and driven by a drive gear or other drive means. The shaft is supported on spaced sealed bearings carried in a housing with back-up or additional lubrication by oil flow from the associated engine oil system. Both ball and roller bearings have been used in the past to carry rotary support loads and axial thrust forces acting on the shaft.
Existing water pumps have a typical life expectancy of about two to three years with the primary failure modes being bearing failure and seal failure. The bearing failures are typically caused by either loss of bearing lubrication, contamination of the bearing lubrication, or leakage of water into the bearing compartments. The seal failure mode is typically caused by failure of the rotating water seal spinning against the stationary seal component on the impeller side of the pump.
In order to prevent the escape of pressurized water from the impeller end of the pump into the oil lubricated portions of the pump, a specific prior art pump system utilizes an antimony carbon seal spinning against a stationary metallic bushing. Both the antimony carbon seal and the metallic bushing are relatively soft materials prone to wear and exhibit problems maintaining a secure leak proof seal in a water pump function. Although these materials have historically been part of pump designs, they have not been able to meet the extended life expectations of pumps in modern mechanical systems.
At least one prior art water pump has attempted to increase the life of the water pump by ensuring that a sufficient supply of oil is provided to the bearings. In this prior art water pump (not shown), the bearings of the water pump are lubricated by grease in the bearings and within the housing by oil delivered through a feed passage. The passage receives lubricating oil from a lubricated portion of an associated engine on which the pump is mounted and directs the oil into an annular chamber or enclosure from which it may lubricate both bearings. Excess oil in the enclosure can escape either by passing through the drive bearing into the adjacent engine enclosure or by passing through the impeller bearing into an annular collector groove. The groove connects with a drain line or passage that carries oil from the collector groove back to the associated engine oil system for return to the engine sump. An oil control combines an oil slinger, a stationary deflector and a lip oil seal with a return passage to the engine to prevent oil from escaping from the bearing enclosure into the water side of the pump housing. However, this prior art pump does not prevent contamination and heat in the engine oil from adversely affecting the bearing life of the pump.
Another problem with the prior art pumps is the mechanical failure of the shaft and impeller caused by torsional stresses along the keyway slots formed in each to allow the keyway to secure the impeller to the shaft.